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| Home > Publications database > Untersuchung der Deaktivierung von Katalysatoren für die Methanolsynthese aus Kohlendioxid und Wasserstoff |
| Home > Publications database > Untersuchung der Deaktivierung von Katalysatoren für die Methanolsynthese aus Kohlendioxid und Wasserstoff |
| Book/Report | FZJ-2019-00548 |
1995
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/21318
Report No.: juel-3057
Abstract: In this work the reasons for the deactivation of a Cu/ZnO/Al$_{2}$O$_{3}$ catalyst used in methanol synthesis from carbon dioxide and hydrogen were investigated. Experiments in a differential recycle reactor showed that the water partial pressure dominates the ageing process. There is a reversible and an irreversible effect of water on the catalyst. With different analytical methods (measurement of copper and total surface area, XRD, XPS, in situ surface enhanced raman spectroscopy) the microscopic reasons of the deactivation were investigated. In the first 300-400 hrs time-on-stream the catalyst lost a substantial amount of it's copper surface area. According to the prevalent opinion in the literature, the acitve centers of methanol synthesis are located on the copper surface. Afterapproximately 400 hrs time-on-stream the reaction rate and the copper surface area remained nearly constant. During the phase of rapid deactivation, i. e. at 50, 100 and 250 hrs time-on-stream, a new copper phase and a new zinc phase emerged simultaneously on the catalyst surface. At 400 hrs time-on-stream they had disappeared again. The amount of these new phases was always strictly correlated with the partial pressure of water. Probably these two new phases consist of a Cu$^{+}$-nonolayer on ZnO. A mechanism for the water-enhanced sintering of the copper phase of the catalyst is suggested. This mechanism is based on the mobilization of Cu$^{+}$-ions by adsorbed water clusters.
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